A communication system including a plurality of communication devices is known. As one of this type of communication systems, a communication system disclosed in Patent Document 1 assigns a communication path to a traffic flow condition.
Herein, a communication path is configured by connection of a communication device serving as a starting-point device and a communication device serving as an end-point device in a state of being cable of communicating via at least one relay-point device. A relay-point device is a communication device other than a starting-point device and an end-point device. Moreover, a traffic flow condition contains a condition for determination of a communication device of the source of transmission and a communication device of the destination of transmission.
The communication system transmits communication traffic which satisfies a traffic flow condition so that the communication traffic passes through a communication path assigned to the traffic flow condition.
As provided in IEEE802.1AX of IEEE (the Institute of Electrical and Electronics Engineers, Inc.) standards, a technique of using a plurality of communication lines as one virtual communication line, namely, link aggregation is known.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2001-082858
With this technique, a section available band, which is a communication band available in a section between communication devices adjacent to each other in a communication path, often varies for each section. However, with the abovementioned communication system, it is impossible to acquire a section available band of each section, and hence, it may be impossible to transmit communication traffic through an appropriate communication path.